“Prenatal BPA exposure may be associated with [aggressive] behaviors in 2-year-old children, especially among female children, but this study has several limitations,” concluded the report, which was published online Oct. 6 in Environmental Health Perspectives. “The results of these analyses should be interpreted cautiously.”

Specifically, the researchers said a number of “unmeasured [factors] may be responsible for some or all of our observed associations [and that] it is possible we did not adequately assess parental psychology” and how that influenced the behavior of the children in the study.

In addition, they noted that it is “difficult to accurate characterize exposure [to BPA] from a single measurement” and added that they did not examine whether postnatal BPA exposure was associated with childhood behavior.

The study, which looked at the possible effect on early childhood behavior and prenatal BPA exposure, assessed the results of standard behavioral assessment tests given to the children of 249 women whose BPA levels were measured through urine samples 16 and 26 weeks into their pregnancy and at birth.

BPA is used to make polycarbonate baby bottles, in the epoxy resins used to line metal cans, in some medical tubing and in PC products including bicycle helmets and compact discs. According to the Environmental Protection Agency, 93 percent of people in the U.S. have a detectible level of BPA in their urine.

A number of laboratory studies have linked BPA to birth defects, low birth weights, cancer, early puberty and other health problems in rats. However, 11 safety agencies around the world have said that BPA is safe for use in food contact applications.

The Food and Drug Administration is currently reviewing BPA safety and said it will decide by Nov. 30 whether it needs to change its long-held stance that there is not enough data to support a ban on the use of BPA in food packaging — in particular, baby bottles.

Connecticut, Minnesota, Chicago and Suffolk County, N.Y., have banned the sale of PC baby bottles, food containers and cups that contain BPA.

The Suffolk County ban went into effect in July. The Minnesota ban goes into effect Jan. 1, the Chicago ban goes into effect Jan. 31 and the Connecticut ban on Oct. 1, 2011. The Connecticut ban also applies to infant formula cans and all reusable food and beverage containers.

In a phone interview Oct. 7. Steve Hentges, executive director of the polycarbonate/BPA global group of the plastics division of the American Chemistry Council in Arlington, Va., said people should be cautious about drawing definite conclusions from the study published online in Environmental Health Perspectives.

“There is significant potential for this study to be misconstrued, so you need to be very careful about how you look at its conclusions,” Hentges said. “The study cannot be considered meaningful for human health unless the findings are replicated in a more robust study.”

He said the study only evaluates parameters measured in the study for “statistical associations which may be neither real, nor meaningful. It is a very limited study which does not establish cause-effect relationships,” said Hentges. “There are many other things that were not measured” that could cause the results suggested in the study.

Hentges points out, for example, that the study did not evaluate the impact of diet and nutrition on the patterns of behavior, or the influence of parents on the behavior of their children. “Diet and nutrition are important parameters for fetal development.”

But despite the study’s limitation, there is cause for concern, said the study’s lead author, Joe Braun, a doctoral student in the department of epidemiology at the Gillings School of Public Health at the University of North Carolina.

“We wanted to know if there was a risk in humans for neurodevelopment problems” based on prenatal BPA levels, said Braun, as five previous rodent studies have indicated that prenatal BPA exposure is associated with increased aggression. “The study results indicate that exposure to BPA early in the pregnancy seems to be the critical issue.” The researchers did not suggest why the higher BPA levels only affected girls.

“Although this is the first study of its kind, it suggests we may need to reduce exposures [to BPA] during pregnancy,” said the study’s corresponding author, Bruce Lanphear, a pediatrician at BC Children’s Hospital in Vancouver, British Columbia, who is also a professor of children’s environmental health in the health sciences department at Simon Fraser University in Burnaby, British Columbia.

The study was conducted by researchers at UNC, Simon Fraser University and the Cincinnati (Ohio) Children’s Hospital Medical Center, using data from mothers and children in Cincinnati.